1. Field of the Invention
The present invention relates to active-matrix organic electroluminescent (EL) display devices. More specifically, the present invention relates to an organic EL display device having a pixel circuit structure in which a light-emitting circuit and a light-receiving circuit for receiving information are provided for each pixel.
2. Description of the Related Art
Recently, due to the advantages of low power consumption, high response speed, and wide viewing angle, self-illuminating organic EL display devices have attracted attention as output devices. With the recent development of communication environments, high-performance displays capable of displaying motion pictures have been demanded for output devices of mobile terminals, and the use of organic EL display devices is expected. In particular, active-matrix organic EL display devices having integrated thin-film transistors as active elements have been intensively developed; these are disclosed, for example, in Japanese Unexamined Patent Application Publications No. 2001-85160, No. 2002-297096, and No. 2003-118164.
In mobile devices having input and output devices, thin-film resistance-type touch panels have been used as input devices. In a touch panel system that detects a change in potential at a touch point, it is theoretically impossible to detect more than one touch point at the same time, and therefore touch panels are not suitable for game applications. Also, a touch panel disposed on the display surface of a display device causes an increase in thickness of the device and a reduction in brightness of the display.
Recently, mobile phones equipped with a charge-coupled device (CCD) camera or a complementary metal oxide semiconductor (CMOS) camera as an input device have become widespread. Mobile phones having a built-in fingerprint sensor for use in personal authentication have also become commercially available. The sensors used as input devices are not integrally formed with an image display unit, and therefore must be incorporated in limited spaces of the mobile phones.